A new in vitro bioassay will be applied to study colony formation by human tumor stem cells from primary explants. The colony forming assay will be used to study the physical and biological properties of tumor stem cells. Tumor cells from cancer patients' bone marrow aspirates, malignant effusions, and surgical samples of primaries and metastases will be studied from a variety of types of cancer. The fractional survival in vitro of human tumor stem cells to selected anticancer drugs will be studied in specific types of cancer with the aim of developing a predictive approach to cancer chemotherapy.